Step 71: Hardware debugging: Broken LEDs

Step 72: Feedback

We love getting feedback on our projects! The 4x4x4 LED cube has received a ton of feedback, and many users have posted pictures and videos of their...

Step 13: Choose your LEDs

There are many things to consider when choosing LEDs.

1)
You want the LED cube to be equally visible from all sides. Therefore we strongly recommend using diffused LEDs. A clear LED will shoot the majority of it's light out the top of the LED. A diffused LED will be more or less equally bright from all sides. Clear LEDs also create another problem. If your cube is made up of clear LEDs. The LEDs will also partially illuminate the LEDs above them, since most of the light is directed upwards. This creates some unwanted ghosting effects.

We actually ordered diffused LEDs from eBay, but got 1000 clear LEDs instead. Shipping them back to China to receive a replacement would have taken too much time, so we decided to used the clear LEDs instead. It works fine, but the cube is a lot brighter when viewed from the top as opposed to the sides.

The LEDs we ordered from eBay were actually described as "Defused LEDs". Maybe we should have taken the hint ;) Defusing is something you do to a bomb when you want to prevent it from blowing up, hehe.

2)
Larger LEDs gives you a bigger and brighter pixel, but since since the cube is 8 layers deep, you want enough room to see all the way through to the furthest level. We went with 3mm LEDs because we wanted the cube to be as "transparent" as possible. Our recommendation is to use 3mm diffused LEDs.

3)
You can buy very cheap lots of 1000 LEDs on eBay. But keep in mind that the quality of the product may be reflected in it's price. We think that there is less chance of LED malfunction if you buy better quality/more expensive LEDs.

4)
Square LEDs would probably look cool to, but then you need to make a soldering template that can accommodate square LEDs. With 3mm round LEDs, all you need is a 3mm drill bit.

5)
Since the cube relies on multiplexing and persistence of vision to create images, each layer is only turned on for 1/8 of the time. This is called a 1/8 duty cycle. To compensate for this, the LEDs have to be bright enough to produce the wanted brightness level at 1/8 duty cycle.

6)
Leg length. The cube design in this instructable uses the legs of the LEDs themselves as the skeleton for the cube. The leg length of the LEDs must be equal to or greater than the distance you want between each LED.

alternative is to use concave LED's, their usually more expensive and a bit harder to find and even though they are waterclear most of the light is shot sidewards, not up Im using them on my cube that is currently under construction :D

You could use rgb leds, however it would nearly triple your i/o ports, as you need a separate line to drive each color.

Also, you would be severely limited in the number of colors you would actually be able to implement due to digital control. you would have 8 (2^3) color combinations, since each color can only be on or off.

With RGB LEDs you might be able to pulse-width modulate the output to the LEDs to vary the intensity of each color component. It would probably require a really fast microcontroller and drastically complicate the software though.

Is there a difference [on an eletrical requirment level] between different colored LEDs? [i.e. would i need different resistors for red LEDs opposed to green LEDs?] . I ask this because, most of the time, Ive noticed Blue LEDs are brighter than Red LEDs are brighter than green LEDs ect. [within respective brands of course]